An access ceiling, in which a vacant space is formed for allowing access from a top and pipes, wires, cables, ducts, etc. are installed in the vacant space, and then the vacant space is finished by a finishing material such as a panel and the like, is provided at a ceiling of a building. To install the access ceiling, an anchor bolt is used to install various frames such as shaped steels, beams, carrying channels, brackets, pipes, wires, cables, etc. on concrete structures.
A portion of the anchor bolt is buried in the concrete structure, a screw part of the anchor bolt protruding from the concrete structure is fastened to a screw hole, which is drilled beforehand through the frame, or the screw part of the anchor bolt passes through the frame so that the screw part is fastened to the frame. To strengthen the anchorage of the anchor bolt when installing the anchor bolt, and to prevent the anchor bolt from moving to an incorrect position or to an inclined state, fixing apparatus of various structures are being used.
The anchor bolt (insert bolt, hereinafter called insert bolt) will be described with reference to the exploded perspective view of the insert bolt of a related art shown in FIG. 1 and a sectional view showing an example of an installed state of the insert bolt of the related art shown in FIG. 2.
As shown, the insert bolt of the related art includes a bolt shaft 10 provided at an end part thereof with a screw part 12, a spring 40 and a washer W sequentially fitted around the bolt shaft 10, a supporting rod 20 having a supporting rib member 22 having elasticity, and a connecting rod 30, which is inserted last and screwed with the screw part 12.
When a bolt head 14 is pressed and inserted into a hole drilled in a steel structure such as a steel beam and the like while all components are completely assembled, as shown in FIG. 6, the supporting rib member 22 is contracted while the spring 40 is compressed to push the washer 24 upward and the washer is continuously moved upward such that the supporting rib member 22 completely passes through the hole, thereby fastening the insert bolt.
When the supporting rib member 22 completely passes through the hole, as described above, the supporting rib member 22 supports a bottom surface of the hole and the washer W is pushed by the spring 40 to support a top surface of the hole such that the supporting rib member 22 is fixed.
Then, the concrete is casted, and after a predetermined time has elapsed, a component having a screw thread, which can fix other structures from a lower side of the connecting rod 30, is screwed to the connecting rod.
However, the insert bolt of the related art includes the washer W and the supporting shaft 20 which are separate components, so when casting she concrete or external force is applied, the spring 40 is compressed and the washer is fluctuated, thus the bolt shaft 10 is not securely fixed in the hole, but transversely moved.
Specifically, when casting the concrete, if the body of the insert bolt is moved and become inclined, a worker needs to fasten the insert bolt while checking the insert bolt using the eye. If this process is performed carelessly, the inclined construction may be realized, so various problems such as levelling errors wish other structures may occur.
To solve the above described problems, the applicant proposed Korean Registered Utility Model No. 20-0378873 which discloses an insert bolt configured for an accurate installation by clamping a transverse movement even when an external force is applied thereto after the insert bolt is fastened to a hole. The insert bolt, which is installed into a steel structure, includes a bolt shaft 10 having a screw part 12, a spring 40 fitted onto the bolt shaft 10, a washer W, on which a supporting rod 20 is integrated, sequentially fitted onto the bolt shaft 10 after the spring 40, a rib ring R sequentially fitted onto the bolt shaft 10 after the washer W and having supporting rib member 22 corresponding to the washer W, and a connecting rod 30 coupled to the screw part 12, wherein the spring 40, the washer W and the rib ring R are sequentially fitted onto the screw part 10, and then, the connecting rod 30 is fastened to the screw part 12, thereby coupling the insert bolt to the hole.
In the configuration described above, a force may be applied to the bolt shaft and the bolt shaft may be rotated in the process of casting the concrete, thus the bolt shaft and the connecting rod may become released.
In other words, the concrete is casted while the bolt shaft and the connecting rod is screwed, so the pressing force of the concrete is transferred to a bottom surface of the bolt shaft and the bolt shaft vibrates in a counter clockwise direction, thereby releasing the bolt shaft from the connecting rod.
In addition, because there is no structure for adequately dispersing the pressure of the concrete, the proposed structure fails to completely solve the inclination of the bolt head.
In addition, when examining the related art, because the rib ring is slidably coupled to an outer side of the bolt shaft, the rib ring R follows the bolt shaft 10 and is pushed up when the supporting rib member 22 makes contact with an entrance of the hole while the insert bolt is continuously inserted into the hole of the structure such as a steel beam. For this reason, in order to completely couple the insert bolt, the bolt shaft is required to be deeply inserted into the bolt shaft.
In other words, since the rib ring of the related art is slidably coupled, when the insert bolt is inserted into the hole and moved, the rib ring is moved upward by a predetermined height, then the supporting rib member is contracted, so the insertion depth of the insert bolt becomes deeper.